1. Field of the Invention
The invention relates to diagnostics and, more particularly, to a method for diagnosing an electrical connection to a load, where a first voltage for operating the load is produced by a first output of a first output assembly, and a second voltage for operating the load is produced by a second output of a second output assembly, and where in a first step, a test of the electrical connection in the first output assembly is performed through the first output.
The invention furthermore relates to an output assembly having a first output, which is configured to operate a load with a first voltage, having a control device for operating a switching device which switches the first output, and having a measuring device for producing a measured value.
2. Description of the Related Art
Diagnostic methods and assemblies are used, for example, for digital output assemblies, where the diagnosis of the electrical connection preferably amounts to identifying a wire break. Particularly, in the case of safety devices, such as in automation technology, reliable wire break identification plays an important role. On the one hand, safety must be ensured for the process, and on the other hand, safety for life and limb must be ensured, such as for the people involved in the process. Furthermore, in the case of these safety applications, redundant connection of the output assemblies plays a further important role. In the field of automation technology, redundancy means the presence of functionally identical or comparable resources in a technical system when these are not required for fault-free operation, during normal operation. Therefore, at least two systems or two output assemblies are provided to ensure redundant operation.
Based on a redundantly connected system of two conventional automation assemblies, it is known, for example, for the outputs from two digital output assemblies for driving a load to be connected in parallel to the load. Consequently, if one output assembly fails, the current supply for the load is ensured by the other assembly. Here, both output assemblies are equipped with wire break identification. In the situation, in which one of the two assemblies identifies a wire break to the load, the wire break is signaled to the other assembly over a separate communication interface between the redundantly connected output assemblies. This has the disadvantage that additional wiring must be provided for communication between the assemblies. Since the assemblies must also be supplied with an operating voltage, it is also disadvantageous that, in the case of the redundant connection, i.e., in the event of fluctuations in the supply voltages, it is possible for a wire break identification to be diagnosed prematurely, even though no actual wire break has occurred.